[clang] [clang][OpenMP] Emit host diagnostics that were deferred and never flushed (PR #220316)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 58553 tests passed
* 3206 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### SanitizerCommon-Unit
<details>
<summary>SanitizerCommon-Unit._/Sanitizer-x86_64-Test_exe/StopTheWorld/SuspendThreadsAdvanced</summary>

```
Script:
--
C:\_work\llvm-project\llvm-project\build\runtimes\runtimes-bins\compiler-rt\lib\sanitizer_common\tests\.\Sanitizer-x86_64-Test.exe --gtest_filter=StopTheWorld.SuspendThreadsAdvanced
--
C:/_work/llvm-project/llvm-project/compiler-rt/lib/sanitizer_common/tests/sanitizer_stoptheworld_test.cpp:144
Value of: argument.threads_stopped
  Actual: false
Expected: true


```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/220316